Have a library card?
Want free ebooks and/or audiobooks?
Of course you do.
Then try out OverDrive. OverDrive is a service that allows libraries from across the country to download ebooks and audiobooks. Lending periods are typically either 7 or 14 days. I, personally, have just started using this service in the past few months, and I highly recommend it. I have the app for both my Kindle as well as my Droid (found on the Google Play store).
If you're like most people who love to read but cannot afford to buy as many books as you want, then try out OverDrive.